For the purification and sterilization of water, especially drinking water, not only chlorine and other chemicals can be used, but also and especially ozone. Therefore numerous water purification apparatus are already known, which have ozonizers for the production of ozone and have many advantages over conventional apparatus operating with chlorine. Their disadvantage is that heretofore large stationary plants have been used almost exclusively, which involve not only considerable complexity of manufacture and high maintenance costs, but also require the employment of trained operating personnel and therefore high consequential costs. The same applies to plants in which ozone is used for other purposes.
One especially important component of an effective purification plant is the ozonizer, which consists of a gas discharge tube in which ozone is produced by a silent discharge. The gas discharge tube contains two tubular, coaxially disposed electrodes whose confronting surfaces define a discharge zone within which at least one electrode is provided with a dielectric coating of glass or ceramic, and one of which is grounded and the other is connected to a high voltage.
For the production of the high voltage and for the operation of such ozonizers, two kinds of circuits have been used. According to one known proposal (DE-OS No. 2,620,540), a direct current from a mains-operated power supply is converted to electrical pulses by means of a thyristor and an oscillator connected to its control electrode. These pulses are delivered to the primary coil of a high-voltage transformer, such as for example an autotransformer, whose secondary side is connected to the electrodes of the ozonizer. The other known circuit (DE-AS No. 2,610,809) contains a high-voltage pulse generator and two high-voltage DC power supplies.
When a plurality of ozonizers are being operated simultaneously, it is desirable to arrange the circuitry such that it can be adapted individually, by individual control of the duty ratio, i.e., the quotient of the width and period of the pulses produced, so as to be able to operate each of the ozonizers at its best efficiency. This requirement is mainly due to the fact that the ozonizers obtainable on the market are very different and therefore the ozone yield of each ozonizer when connected to a standardized circuit can be very different. When the first-named circuit (DE-OS No. 2,620,540) is used, such adaptation is not possible. The other circuit (DE-AS No. 2,610,809) does contain a pulse generator with an adjustable duty ratio, which could be adjusted individually to adapt the circuit to the ozonizer used in the particular case. Such circuits, however, are on the one hand very complex and, on account of the high costs, they are appropriate only for large plants. On the other hand, if a plurality of ozonizers is used, only the two possibilities exist, either of providing a separate circuit for each individual ozonizer so as to adjust the duty ratio individually by means of each pulse generator, or to operate all of the ozonizers with the same circuit. In the first case, the manufacturing costs would be further increased, which is not acceptable, while in the second case no individual adjustment of the duty ratio would be possible, so that at least some of the ozonizers would be operated at poor efficiency.
As a result of this development, large stationary apparatus have been known, which have to be installed and operated with a great deal of technical complexity and expense, while on the other hand, small and medium apparatus, such as are desirable for small swimming pools, fish breeding tanks or transportable drinking water purification equipment, are operated exclusively with circuits having high-voltage transformers and permit no optimation of the efficiency of the ozonizers.
The invention therefore sets out from a circuit for the pulsed operation of one or more high frequency ozonizers, which has at least one DC power supply, a number of circuits, corresponding to the number of ozonizers, for the derivation of electrical pulses from the direct current, and a number of high voltage transformers corresponding to the number of ozonizers, to whose primaries the pulses produced from each one of the circuits are delivered and whose secondaries are connected each with one ozonizer.
It is the object of the invention to improve this circuit such that, with the use of commonly available and therefore economical components, it will permit a simple and optimum adaptation to the ozonizers used in each case, in accordance with the amounts of ozone desired, will be suitable especially for small and medium capacity ozonizers of up to about ten grams of ozone per hour, and will permit the addition, by modular expansion, of a plurality of ozonizers and hence a corresponding multiplication of the amount of ozone that can be produced.